Polymers which are degraded by a physical or chemical process in response to contact with body fluid, while implanted or injected, are generally considered to be biodegradable. Biodegradable polymers have been the subject of increasing interest as materials which can be employed to form a wide variety of pharmaceutical preparations and other biomedical products. Examples of medical applications for biodegradable polymers include tablet coatings, plasma substitutes, gels, contact lenses, surgical implants, systems for controlled drug release, as ingredients of eyedrops, and as long circulating and targeted drugs.
Many polymers have hydrophobic domains and, consequently, their biocompatability is limited. Hydrophobic polymers are vulnerable to non-specific interactions with proteins and lipids which also may cause undesirable side effects. In addition, synthetic polymers, such as vinyl, acrylic and methacrylic polymers, which typically have a hydrophobic main chain that do not degrade readily in vivo.
Hydrophilic polymers are common in nature. For example, polysaccharides are naturally-occurring polymers which include hydrolytically-sensitive acetals in their main chain. However, polysaccharides can interact with cell receptors and/or plasma opsonins, which can cause adverse reactions and other non-desirable effects.
Polyacetals can be formed synthetically. However, most synthetic polyacetals contain acetal group not in the main chain. Further, known synthetic polyacetals with acetal groups in the main chain are essentially hydrophobic and have limited solubility in water. They also do not include pharmaceutical substituents.
Therefore, a need exists for a polymer which overcomes or minimizes the above-referenced problems.